Stitching is nothing like Hatching. Stiching just gives the appearance of another item with current stats. Even if you allowed pet stitching, you'd still have to hatch and train the correct talents into a pet first. All stitching would do is allow you to have a pet look like another pet but get all the cards and talents of a different one. No real reason for this except for personal preferrences in looks of a pet.
it does not remove the purpose of hatching because it is still the purpose of time vs. crowns. you could look around for a while to find someone to hatch with or just stitch by buying crowns. so i dont think its too bad of an idea.